It is now common practice in the electronics industry to package small integrated circuits on a substrate of ceramic or plastic and provide conductors on the substrate which extend to the marginal side edge portions of the substrate. The connectors for IC packages of this type typically comprise an open rectangular frame having a central well therein which receives the substrate and having contact terminals therein which engage the terminal pads on the substrate when it is positioned in the well. It is necessary to provide some means to ensure that the contact terminals in the connector housing will be urged against the terminal pads on the substrate with a force sufficient to establish electrical connections having the required electrical characteristics for the system and to this end it has become common to provide a separate lid for the connector housing which is assembled to the housing in covering relationship to the substrate. The lid has integral pressure applying springs which bear against the upwardly facing surface of the substrate and thereby maintains the required contact pressure for the terminal pads and the contact terminals. A commonly used type of integrated circuit package accommodates an integrated circuit chip having 68 terminal areas thereon so that the substrate, therefore, has a total of 68 terminal pads positioned in rows along its marginal side edges. The substrate is relatively small, however, it is nonetheless necessary to maintain an adequate contact force at each electrical interface of a terminal to one of the terminal pads on the substrate. The spring means in the lid must therefore be capable of developing relatively high forces and imposing these forces on the substrate in order to maintain and develop these contact forces. The present invention, in accordance with one aspect thereof, is directed to the achievement of a lid having improved spring means for biasing the substrate of an IC package against the terminals in a connector.
It is also common practice in connectors of the type described above to provide a biasing means in the connector housing which bears against one corner of the IC package substrate and biases it to a precisely predetermined position in the connector so that the terminals in the connector will be in engagement with the terminal pads on the substrate. In accordance with present practice, this biasing means is commonly provided as a separate spring device in the connector housing, see U.S. Pat. No. 4,220,383. While this method of biasing the IC substrate to its proper position in the connector is satisfactory, it would be desirable to eliminate the separate spring in the housing for this purpose, and thereby simplify the construction of the connector assembly. The present invention, in accordance with a further aspect thereof, is directed to the achievement of a housing lid having an integral biasing means in combination with a suitable pressure spring means so that the need for a separate biasing spring in the housing is eliminated.
One form of clamping lid in accordance with the invention comprises a flat stamped and formed sheet metal member which is dimensioned to be mounted on the housing in covering relationship to the IC package and which has along three of its sides, a pair of overlapping cantilever springs which extend towards each other and parallel to the sides of the sheet metal member. The springs are generally triangular and each spring extends from a location adjacent to one of the corners of the sheet metal member towards an adjacent corner and past the associated spring which extends from the adjacent corner. By virtue of the provision of these three pairs of springs along three of the sides of the member, clamping forces are applied to the substrate at six locations distributed around the periphery of the substrate. An individual clamping spring is provided adjacent to the remaining side of the rectangular member and, in addition, a substrate biasing arm is formed adjacent to this single spring. The biasing arm is in the form of a cantilever having a laterally directed free end which is formed such that when the lid is assembled to a housing in which an IC package has been placed, the free end of the biasing arm engages one corner of the substrate and pushes it to a precisely predetermined location in the housing while the lid is being placed on the housing. After the substrate has been so positioned, the springs in the lid move relatively against the surface of the substrate and apply the clamping force against the substrate, which is required to ensure adequate contact force at each of the electrical interfaces of the contact terminals in the housing in the terminal pads on the IC package substrate.